systems, electron transfer can be investigated with an approach similar to that
described here.
6 Concluding Remarks
In summary, 2DRR spectroscopy can be used to expose correlations between
reactants and products in ultrafast photochemical reactions. These types of
correlations cannot be revealed by traditional third-order methods such as transient
absorption and photon echo spectroscopy in which reactions must be initiated from
equilibrium conditions. Experimental tests show that 2DRR signals will generally
be larger than cascaded nonlinearities for solutions with optical densities less than
1.0 [22, 24]. Model calculations suggest that Franck–Condon activity obviates the
selection rules that promote artifacts under electronically off-resonant conditions
[22]. Our experimental investigation of the photodissociation reaction of triiodide
demonstrates that the information content of a 2DRR spectrum can be controlled by
varying laser beam geometries and the colors of the pulses in the sequence. Results
summarized in this article suggest that the bond length of the triiodide reactant is
correlated to the distribution of vibrational quanta in the diiodide product [23].
The 2DRR technique can be used to probe the general vibronic coherence
transfer process defined in Fig. 1 provided that the photoinduced reaction is faster
than or comparable to the vibrational period(s). Thus, the 2DRR method can also be
applied to vibronic coherence transfer in ultrafast energy and electron transfer
transitions. For example, it may be interesting to apply 2DRR spectroscopy to
ultrafast energy transfer processes in light harvesting proteins [14–16]. In these
systems, the role played by vibronic effects in Frenkel exciton delocalization and
energy transport has generated significant interest in recent years, and some issues
remain unsettled [14, 67–72]. Notably, Harel and co-workers are making significant
steps in this direction with a multidimensional method that is related to 2DRR
spectroscopy [33, 34]. Electron transfer processes offer practical advantages that
will facilitate decomposition of the 2DRR nonlinearity. Most importantly, the
oxidized and/or reduced species in an electron transfer reaction often absorb light in
different regions of the spectrum. Therefore, for some systems, the pathway defined
in Fig. 1 may be readily isolated with multi-color pulse sequences (i.e., the same
approach that we have taken for triiodide). In contrast, the electronic resonances of
the donor and acceptor in an energy transfer transition usually possess significant
overlap, thereby challenging an approach in which pathways are distinguished by
tuning the wavelengths of the laser pulses.
Acknowledgements This work is supported by the National Science Foundation under CHE-0952439
and CHE-1504350.
Top Curr Chem (Z) (2017) 375:87
123
267
Reprinted from the journal
described here.
6 Concluding Remarks
In summary, 2DRR spectroscopy can be used to expose correlations between
reactants and products in ultrafast photochemical reactions. These types of
correlations cannot be revealed by traditional third-order methods such as transient
absorption and photon echo spectroscopy in which reactions must be initiated from
equilibrium conditions. Experimental tests show that 2DRR signals will generally
be larger than cascaded nonlinearities for solutions with optical densities less than
1.0 [22, 24]. Model calculations suggest that Franck–Condon activity obviates the
selection rules that promote artifacts under electronically off-resonant conditions
[22]. Our experimental investigation of the photodissociation reaction of triiodide
demonstrates that the information content of a 2DRR spectrum can be controlled by
varying laser beam geometries and the colors of the pulses in the sequence. Results
summarized in this article suggest that the bond length of the triiodide reactant is
correlated to the distribution of vibrational quanta in the diiodide product [23].
The 2DRR technique can be used to probe the general vibronic coherence
transfer process defined in Fig. 1 provided that the photoinduced reaction is faster
than or comparable to the vibrational period(s). Thus, the 2DRR method can also be
applied to vibronic coherence transfer in ultrafast energy and electron transfer
transitions. For example, it may be interesting to apply 2DRR spectroscopy to
ultrafast energy transfer processes in light harvesting proteins [14–16]. In these
systems, the role played by vibronic effects in Frenkel exciton delocalization and
energy transport has generated significant interest in recent years, and some issues
remain unsettled [14, 67–72]. Notably, Harel and co-workers are making significant
steps in this direction with a multidimensional method that is related to 2DRR
spectroscopy [33, 34]. Electron transfer processes offer practical advantages that
will facilitate decomposition of the 2DRR nonlinearity. Most importantly, the
oxidized and/or reduced species in an electron transfer reaction often absorb light in
different regions of the spectrum. Therefore, for some systems, the pathway defined
in Fig. 1 may be readily isolated with multi-color pulse sequences (i.e., the same
approach that we have taken for triiodide). In contrast, the electronic resonances of
the donor and acceptor in an energy transfer transition usually possess significant
overlap, thereby challenging an approach in which pathways are distinguished by
tuning the wavelengths of the laser pulses.
Acknowledgements This work is supported by the National Science Foundation under CHE-0952439
and CHE-1504350.
Top Curr Chem (Z) (2017) 375:87
123
267
Reprinted from the journal